Computers and backups - looking for pearls of wisdom from the more experienced

[Blackcrusader]

I probably will pick up another used Perdix AI without the transmitter as a backup. Not the least expensive way to go. Diving, Private Airplanes, and Boats are not the 3 cheapest hobbies in the universe.
= Bring Out Another Thousand. Diving is hand-delivering that money to the water.

I was referring to the Suunto's single strap.

Ah so. Mine never failed either on the Suunto as the Suunto died first after I think 4 years of use.

 

[Blackcrusader]

I will look it up when I get the computer out of the box and start setting it up.

Another feature you may like is the "Clear" function. It shows the additional time after you have completed the deco or safety stop.
Often on dives I spend time taking photos or video at shallower than safety stop depth. However I have had a couple of guides DM's instructors point at the time thinking I still had a long time to clear my safety stop as they are not Shearwater users. They think I did some deco time and had to do a longer stop lol.

They insisted I stay down longer to clear the safety stop only to see the time actually increase and not decrease. Privately I am amused and eventually surface to tell them what the time actually means.

 

[KenGordon]

My "happy spot" on dives is 20 to 45 feet of water.

I am going to ignore that for the body of this post. You don’t even need a computer if this is really what you are doing. Follow the guide, you will be fine.

Somewhere around North of $500 USD / day on a typical week long trip with 5 days of diving. Depending on where you are going and the cost of getting there it might be more or less.

$500/day for shallow sites?

Since you don’t want to do any trimix or CCR a Shearwater Peregrine will be ideal. You already have AI on the first computer. If you insist on a removable battery then you have to have a Perdix. You seem to prefer the removable battery but I find the battery indicator on my one is a bit rubbish and have had it die mid dive. By contrast the coil cell style battery on a mono LCD computer lives for a year at least and properly lets you know it is on the way out. So the rechargeable vs AA isn’t so clear cut once you start using it.

These are the Sharewater backup analogue dive computers to go along with your tables. A rec and a tech version. Batteries not required.



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This is the textbook scheme for proper diving. I suspect many on this thread are unaware of what proper planning looks like.

The way it worked was you plan a dive up front.

Say you know you are diving a 40m wreck you’d figure out how long you could do by planning various times and seeing how much gas you’d need. This gets easier with a deco gas as there is generally plenty and all you have to do is figure out the backgas. Anyway by some means you decide to do say 30 minutes and some deco plan like 1/2/5/23 minutes on some gas the cool kids like. You also end up with a limit based on back gas pressure.

You put that plan on a slate, along with some deeper/longer plans incase you make a mistake Or something unexpected happens.

In the water a timer/depth gauge combo (aka bottom timer) lets you follow the plan. As backup you have two timers.

This is pretty time consuming and not flexible. If the wreck is not flat then some of the time will be shallower and you still need to leave the bottom at 30 minutes and then do all the same deco regardless. If instead you use a computer you get to stay longer (caution required regarding back gas) and do the actual deco. The trouble is what happens if that computer fails? Now you have to get back to the slate plan using the bottom timer but do not know if you exceeded the envelope of that plan. Thus in such a scheme you can not extend bottom time if doing well on gas or it is actually a bit shallower. You could take some extra “just shallower/just longer plans” but people don’t/didn’t.

So the answer is to have two similar(ish) computers each capable of getting you out of the water. (Or assume your buddy will have a similar profile but that is frowned upon.)

It can take a lot of lying to yourself to risk lying to your significant other about why you MUST have the toy peer pressure says is the cool toy today or covering it up. One particular lie popular on SB is that you should ”buy once cry once” and so, in this context, buy a £1000 computer at the start when you have no idea what is what yet. Everyone who is not doing trimix or doesn’t have £2k to burn will be better to have two Peregrines. So start with the cheap option and add trimix/CCR later. For CCR you only need one standalone computer as backup so you actually never need to own two stupidly expensive computers.

I usually dive a rebreather with a Petrel as the primary and a Perdix as a backup. Before I bought the Perdix I used a HelO2 as the backup. Before the rebreather I used the HelO2 as the main computer and a Zoop as the backup (some times bending the Zoop so it was essentially a bottom timer) with a slate.

For OC deco diving I now use the Perdix as the primary computer and the HelO2 as the backup.

There are many ways to improve your enjoyment of diving more than buying an expensive computer. Drysuits, holidays, etc. For the price of a Teric and transmitter or two Perdix AIs you could do both ANDP and 60m Trimix. The Garmin and in some markets the Suunto Eon Steel are equally expensive, this is not an anti Shearwater thing, more an anti received wisdom thing.

 

[Gareth J]

properly lets you know it is on the way out. So the rechargeable vs AA isn’t so clear cut once you start using it.



This is the textbook scheme for proper diving. I suspect many on this thread are unaware of what proper planning looks like.

The way it worked was you plan a dive up front.

Say you know you are diving a 40m wreck you’d figure out how long you could do by planning various times and seeing how much gas you’d need. This gets easier with a deco gas as there is generally plenty and all you have to do is figure out the backgas. Anyway by some means you decide to do say 30 minutes and some deco plan like 1/2/5/23 minutes on some gas the cool kids like. You also end up with a limit based on back gas pressure.

You put that plan on a slate, along with some deeper/longer plans incase you make a mistake Or something unexpected happens.

In the water a timer/depth gauge combo (aka bottom timer) lets you follow the plan. As backup you have two timers.

This is pretty time consuming and not flexible. If the wreck is not flat then some of the time will be shallower and you still need to leave the bottom at 30 minutes and then do all the same deco regardless. If instead you use a computer you get to stay longer (caution required regarding back gas) and do the actual deco. The trouble is what happens if that computer fails? Now you have to get back to the slate plan using the bottom timer but do not know if you exceeded the envelope of that plan. Thus in such a scheme you can not extend bottom time if doing well on gas or it is actually a bit shallower. You could take some extra “just shallower/just longer plans” but people don’t/didn’t.

So the answer is to have two similar(ish) computers each capable of getting you out of the water. (Or assume your buddy will have a similar profile but that is frowned upon.)

It can take a lot of lying to yourself to risk lying to your significant other about why you MUST have the toy peer pressure says is the cool toy today or covering it up. One particular lie popular on SB is that you should ”buy once cry once” and so, in this context, buy a £1000 computer at the start when you have no idea what is what yet. Everyone who is not doing trimix or doesn’t have £2k to burn will be better to have two Peregrines. So start with the cheap option and add trimix/CCR later. For CCR you only need one standalone computer as backup so you actually never need to own two stupidly expensive computers.

I usually dive a rebreather with a Petrel as the primary and a Perdix as a backup. Before I bought the Perdix I used a HelO2 as the backup. Before the rebreather I used the HelO2 as the main computer and a Zoop as the backup (some times bending the Zoop so it was essentially a bottom timer) with a slate.

For OC deco diving I now use the Perdix as the primary computer and the HelO2 as the backup.

There are many ways to improve your enjoyment of diving more than buying an expensive computer. Drysuits, holidays, etc. For the price of a Teric and transmitter or two Perdix AIs you could do both ANDP and 60m Trimix. The Garmin and in some markets the Suunto Eon Steel are equally expensive, this is not an anti Shearwater thing, more an anti received wisdom thing.

@KenGordon 's post is an excellent post.

Prior to purchasing my CCR in 2004. I did a lot of hard table Trimix diving. As Ken outlined, the dive was preplanned and the decompression schedule was written on to wet notes and a slate. This included gas loss plans. This was the same approach i used for the ERD dives.
I did have a Suunto Vyper (set to Gauge mode), and a Suunto Vytec, which was either set to 3 gas mode (ERD dives), or Gauge Mode (Trimix).

When I got the CCR, it had its own built in decompression computer. The big recommendation was to get a VR3 as a backup. Which was another £1k. I didn't, I used the Vytec and switched gases at specified depths (PO2) related, and a Hard Table (CCR). I had a general set of Hard tables I created for CCR diving.
Mainly because most of my diving was with OC buddies I did this for years. My most recent backup computer was an OSTC. I used the same practice.
I have long since upgraded the unit to the more modern (full colour) controller and computer.

I have only recently invested in a new Shearwater, partly for the CCR features. Partly because I wanted a new toy.

I strongly believe investing in a top of the range computer when you start diving is generally a fools investment. Computer capabilities, current best decompression practice, change quite rapidly.
The Vytec (1999/2000), was pretty edge at the time, although a VR3 (at considerably more cost), was the most capable at the time.
Not only is the VR3 decompression model somewhat dated, it was very difficult to use. Rather than investing in a VR3 in 2005, a new diver would have done better to go diving, and invest in a more modern computer 5 years later. Technology, best practice, and decompression theory move very quickly.

 

[Blackcrusader]

I am going to ignore that for the body of this post. You don’t even need a computer if this is really what you are doing. Follow the guide, you will be fine.

This is the textbook scheme for proper diving. I suspect many on this thread are unaware of what proper planning looks like.
The way it worked was you plan a dive up front.

This is not an anti Shearwater thing, more an anti received wisdom thing.

Great post thanks. I learned deco diving on air before computers and nitrox were available in the 1980's. Showing my age lol

Nanohawk already bought a Perdix so he has a great DC that perhaps one day he might use for more advanced recreational diving. He wrote he hasn't dived for 7 years so that is a significant loss of skillset so he did mention doing refresher courses.
For some money is no object so they buy what they want. Nanohawk wants to understand GF factors but on 20 - 45 foot dives really nothing to learn for such shallow depths and his dive times he wrote were only 45 mins to an hour. No chance of exceeding NDL on such shallow dives. Surf GF and GF won't be an issue.

One thing that did concern me was this reply by Nanohawk

"I get to dive a couple weeks a year in nice water, so I don't want a repeat where I get locked out because of a computer failure or malfunction. I really have no idea what I did to get locked out and chalked it up to computer misbehavior. "

Yup I have seen plenty of divers get locked out who blame the DC for it's behaviour. They never stop and really understand what they did to cause the DC to lock them out. Usually on a Suunto to get locked out you went into deco and ignored a deco obligation. I've seen that happen when divers fail to pay attention to their DC and just follow others assuming they never need to bother checking their own DC. When my Suunto failed on the pressure sensor that was different than a lockout.

 

[nanohawk]

Great post thanks. I learned deco diving on air before computers and nitrox were available in the 1980's. Showing my age lol

Nanohawk already bought a Perdix so he has a great DC that perhaps one day he might use for more advanced recreational diving. He wrote he hasn't dived for 7 years so that is a significant loss of skillset so he did mention doing refresher courses.
For some money is no object so they buy what they want. Nanohawk wants to understand GF factors but on 20 - 45 foot dives really nothing to learn for such shallow depths and his dive times he wrote were only 45 mins to an hour. No change of exceeding NDL on such shallow dives. Surf GF and GF won't be an issue.

Folks get confused easily...... I like taking pictures in the shallower depths. More interesting corals and small fish there. Great ambient light. I can and will go deeper if there is a reason to.

I am going to ignore that for the body of this post. You don’t even need a computer if this is really what you are doing. Follow the guide, you will be fine.

Please show me where I said that I never go below 45 feet. I'll wait. Better yet, hold your breath while you find it.

$500/day for shallow sites?

To get your cost per dive you need to factor everything directly related to the trip. The trip cost, the airfare, "park fees" and other taxes. By the time you are done you're going to be in the $2.5k USD or better rate pretty quickly. Most week long trips involve 5 days of diving. It's just a number. If you run down to the local pier and jump in it may cost you quite a bit less. In which case you probably are willing to invest quite a bit less in redundancy to be able to keep diving.

Since you don’t want to do any trimix or CCR a Shearwater Peregrine will be ideal. You already have AI on the first computer. If you insist on a removable battery then you have to have a Perdix. You seem to prefer the removable battery but I find the battery indicator on my one is a bit rubbish and have had it die mid dive. By contrast the coil cell style battery on a mono LCD computer lives for a year at least and properly lets you know it is on the way out. So the rechargeable vs AA isn’t so clear cut once you start using it.

Isn't it easier to just side step the whole battery issue by changing it before you need to depend on the estimated charge state? All the computer is doing is reading the output voltage. That's fine on alkaline and lead acid. They have a pretty predictable relationship between resting voltage and charge state. Nimh and Li-ion batteries have a flatter discharge profile and are prone to "falling off" quite rapidly towards the end of it.

Why would someone wait until the battery is almost dead on important equipment to deal with it?

It can take a lot of lying to yourself to risk lying to your significant other about why you MUST have the toy peer pressure says is the cool toy today or covering it up. One particular lie popular on SB is that you should ”buy once cry once” and so, in this context, buy a £1000 computer at the start when you have no idea what is what yet. Everyone who is not doing trimix or doesn’t have £2k to burn will be better to have two Peregrines. So start with the cheap option and add trimix/CCR later. For CCR you only need one standalone computer as backup so you actually never need to own two stupidly expensive computers.

It's really much simpler to use a different justification.

1) Do you want it? 2) Can you afford it? If the answer is yes and yes then do it. Most of this stuff is not like fine dining. It has residual value if you later decide you are done with it and want to sell it.

I usually dive a rebreather with a Petrel as the primary and a Perdix as a backup. Before I bought the Perdix I used a HelO2 as the backup. Before the rebreather I used the HelO2 as the main computer and a Zoop as the backup (some times bending the Zoop so it was essentially a bottom timer) with a slate.

For OC deco diving I now use the Perdix as the primary computer and the HelO2 as the backup.

There are many ways to improve your enjoyment of diving more than buying an expensive computer. Drysuits, holidays, etc. For the price of a Teric and transmitter or two Perdix AIs you could do both ANDP and 60m Trimix. The Garmin and in some markets the Suunto Eon Steel are equally expensive, this is not an anti Shearwater thing, more an anti received wisdom thing.

I will agree there are some other computers on the market, but the price range wasn't that wide that any savings would be financing my next vacation to dive paradise. I wanted to go with hoseless air integration. I wanted a larger screen to make it easier to read. That narrowed the field pretty quickly. $500+transmitter puts you in the ball park of $750 to $850 depending on the manufacturer. The high-end was $1850 (garmin). Now if you go with a console you can get down to $600 for an Oceanic Pro-Plus 3 which looks like a slightly improved version of my Smart Com (buttons instead of contacts).

Most of the hoseless AI computers are clustered in $1K to $1350. That really isn't that much of a variance. I don't know if I would buy a used computer from many of the brands. I was comfortable enough with Shearwater's support that I did buy a used unit for $850 with the sender from someone on SB. Shearwater is one of the only brands that states on it's website that the warranty is on the unit, not the buyer and they support it just the same regardless of where you bought it. Without the transmitter they go for less. Worst case is I buy one with another transmitter and sell the transmitter to someone else. Shrug.

I think the Suunto EON Core was $1164. A new Perdix AI goes for $1350-1399. $250 just doesn't seem like much in this hobby.

 

[Centrals]

We all have different requirement for equipment in diving.
As for DC? My taste is very simple: two cheapo.
24yrs old Aladin pro nitrox with no back light is my work horse, back up by a cheap Oceanic. How difficult it is to shine my torch on the Aladin to check the depth, ndl and time during night dive?

$250.00? I could buy 3-4 HKG/MNL return pre-covid. It is all relative.

 

[KenGordon]

Why would someone wait until the battery is almost dead on important equipment to deal with it?

The Perdix has green, yellow and red battery indicators. When it failed on me it had been green the day before, was yellow on the RIB and dead twenty minutes into the dive. I always change when it goes yellow but not on a small boat.

I think the Suunto EON Core was $1164. A new Perdix AI goes for $1350-1399. $250 just doesn't seem like much in this hobby

Suunto Vyper Novo Light Wrist Computer

Integrating all of the same great features you already expect out of the original Vyper Novo, Suunto's Vyper Novo Light is a pared down version that comes nitrox and free-dive ready. Suunto subtracted

www.leisurepro.com

$350 for a Vyper another $400 ish for a transmitter. Then have a Peregrine and you get everything you need for the price of one Perdix and transmitter.

 

[tursiops]

The Perdix has green, yellow and red battery indicators. When it failed on me it had been green the day before, was yellow on the RIB and dead twenty minutes into the dive. I always change when it goes yellow but not on a small boat.

What kind of battery?

 

[Blackcrusader]

Folks get confused easily...... I like taking pictures in the shallower depths. More interesting corals and small fish there. Great ambient light. I can and will go deeper if there is a reason to. Please show me where I said that I never go below 45 feet. I'll wait. Better yet, hold your breath while you find it.

Not sure if you have read this thread about GF

Gradient Factors and recreational diving

I am looking at transitioning into a computer that uses Gradient Factors. I have superficially read some data on the theory and have a basic idea of theory. I currently use an Oceanic computer set to DSAT and run it pretty close with EAN. Last week in CZM I did 24 dives (26 hours) with most...

scubaboard.com

Yes we all noted you wrote that you dive to deeper depths at times just that most of your dives are in your happy 20 - 45 feet.
Just saying you don't need a DC if you are only diving shallow dives. In fact a DC not really needed for your 45 minute dives even if you had a square profile to 20m 65 feet. So from very shallow to 65 feet deep dives a DC is great to log your dives but not essential. Plenty of vacation divers do dives like that without owning a DC. When my Suunto failed halfway through a dive vacation I did pretty much that unless doing a deeper dive which I would dive plan.

Anyway the Perdix is a great DC even if some think it's a bit wasted just for shallow diving within NDL limits. Most of my dives are NDL and I own a Perdix. But it's good for my Deco dives or even for gas planning NDL dives if I want to. Some people prefer cheaper gear for me cost was not an issue. At the time my Suunto failed I had not had corrective eye surgery and the Perdix was a thing of joy to be able to see the screen so easily especially on night dives. One of the reasons I bought it was the large screen and like you I do not wear a watch.